Wound dressings

ABSTRACT

A wound dressing comprises a wound-contacting layer composed of a mixture of honey and a moisture-absorbing agent; a water-permeable fabric backing layer; and an intermediate layer comprising water-permeable fabric impregnated with a mixture of honey and a moisture-absorbing agent.

FIELD OF THE INVENTION

This invention relates to wound dressings containing honey.

It has been long known that honey possesses antimicrobial propertiesthat make it suitable for use in treating a range of infections and skindisorders. This antimicrobial activity can be attributed to a number offactors, in particular the natural presence in honey of hydrogenperoxide (H₂0₂), its high saccharide content (which tends to dehydratebacteria by osmosis) and its relative acidity (normally around pH 4).Additionally, those honeys produced by bees that have fed on nectar frommanuka blossom possess enhanced antimicrobial potency, due to thepresence in such honeys of an as yet unidentified substance known simplyas “unique manuka factor” (UMF).

The antimicrobial properties possessed by all honeys (and particularlythose containing UMF) also render honey suitable for use in the dressingof wounds, where it assists in preventing infection, the debridement ofnecrotic tissue, the deodorising of malodorous wounds and theminimisation of scar formation. However, an obvious problem associatedwith the use of honey in such circumstances is that it is a rather runnysubstance, with the result that the use of natural honey in a wounddressing is messy and impractical and the wound dressing has noabsorbing capacity, so that on an exuding wound it rapidly becomesunevenly liquefied and runs off the wound. This

BACKGROUND ART

Attempts have been made in the past to overcome this problem bycombining honey with viscosity-enhancing additives. Several suchformulations are mentioned in WO 01/41776. WO 00/09176 discloses a woundtreatment composition comprising an adsorbent material for adsorbingmoisture on or around a wound and a saccharide or polysaccharide orderivative thereof. WO 02/00269 (published on 3^(rd) Jan. 2002) alsodiscloses a wound dressing comprising a honey composition and a basematerial and optionally further layers for adhesion.

DISCLOSURE OF THE INVENTION

We have carried out experimental work that has confirmed that it ispossible to create a moisture-absorbing agent (such as sodium alginatepowder) and allowing the mixture to set. When sheets of such materialwere subjected to a “Paddington Cup test” (as described in the 1996Addendum to the British Pharmacopoeia, p1943), in which a salinesolution is applied to the upper surface of a sample sheet clampedbetween a pair of flanges, it was found that the material readily breaksdown and that saline passes through the sheet in less than 24 hours.Saline liquid also passes through a fabric layer in the same test inless than 24 hours. It has further been found that a fabric impregnatedwith pure honey is liquid water-permeable. Most surprisingly in view ofthese findings, however, it was discovered that a three-layer structurein which a honey-containing sheet of the type mentioned above issupported by a water-permeable fabric backing layer, with anintermediate layer of fabric impregnated with the honey mixture, can besubstantially impervious to liquid water and aqueous saline liquid.Moreover, such substantially liquid-impervious composite material stillhas a significant liquid-absorption capacity, together with a highdegree of permeability to water vapour generally, being capable ofachieving a 24-hour moisture-vapour transmission rate of at least 20 gper 100 cm² and a 24-hour total fluid handling capacity of at least 35 gper 100 cm².

In the context of this invention, the term “impervious” is used inrelation to the composite structure in the sense that liquid water (oran aqueous liquid such as saline solution) does not penetrate all theway through the structure and emerge in the liquid phase at the oppositeface. The above-mentioned “Paddington Cup test” can serve as a test forthis purpose, a composite being considered impervious if the liquidsaline does not pass through it within 24 hours under that test.

The composite material is therefore ideally suited for use as a moistwound dressing, which assists in the healing of exuding wounds, since itretains its structural integrity in moist conditions, is able to form abarrier to liquid water, and yet both absorbs liquid water and transmitssubstantial amounts of water vapour at a steady rate. Both liquidabsorbency and vapour transmission can be important. Absorbed liquidwill include other wound fluid components and wound debris, as well aswater. Moisture vapour transmission is an on-going property of thedressing whereas liquid absorption (absorbency) is a property whichattains a maximum level.

The invention therefore provides, in one aspect, a wound dressingcomprising: a wound-contacting layer composed of a mixture of honey anda moisture-absorbing agent; a water-permeable fabric backing layer; andan intermediate layer comprising water-permeable fabric impregnated witha mixture of honey and a moisture-absorbing agent. The wound dressingsof the invention preferably are substantially impervious to liquid waterbut permeable to water vapour as manufactured, preferably even aftersterilisation.

Generally speaking the wound-contacting and intermediate layer are indirect physical contact as are the intermediate layer and backing layer,although liquid and vapour contact is sufficient.

To provide structural integrity and strength, the honey mixture in thewound-contacting and intermediate layers preferably forms a continuum,as does the fabric in the backing and intermediate layers. In otherwords, the wound-contacting layer and the intermediate layer preferablyform a first continuous phase and the fabric layer and intermediatelayer preferably form a second continuous phase, the first and secondcontinuous phases overlapping to form the intermediate layer. This maybe achieved, for example, by spreading the honey mixture over a layer offabric and allowing the mixture only partially to impregnate the fabricbefore it sets. This structural integrity also assists in removal of aused dressing in one piece.

The invention therefore provides, in another aspect, a method ofmanufacturing a wound dressing, comprising the steps of: providing alayer of a water-permeable fabric material; providing a mixture of honeyand a moisture-absorbing agent; spreading said mixture over said fabriclayer; allowing a portion of said mixture to impregnate an uppersub-layer of said fabric layer; and allowing said mixture to set;thereby producing a dressing comprising a wound-contacting layercomposed of a mixture of honey and a moisture-absorbing agent, awater-permeable fabric backing layer, and an intermediate layercomprising fabric impregnated with said mixture of honey andmoisture-absorbing agent.

In preferred embodiments, the three-layer structure is well defined,with the wound-contacting layer being free (or substantially free) fromfibres such as fabric fibres from the backing layer and the fabricbacking layer being free (or substantially free) from honey. Thethickness of the intermediate layer e.g. as formed by partialimpregnation of the fabric backing layer by the honey mixture may, forexample, be from 100 μm to 1,000 μm, preferably from 200 to 500 μm.

Preferably, the honey layer forms a substantially homogeneous solidphase gel sheet. To ensure this, the ratio of honey tomoisture-absorbing agent in the wound-contacting layer needs to becontrolled within certain limits. Generally, the weight ratio ofmoisture-absorbing agent to honey should be within the range from 1:2 or1:3 to 1:14 and preferably in the range from 1:2 or 1:3 or 1:4 to 1:10.

The preferred ratio of moisture-absorbing agent to honey has been foundto be affected by irradiation, which is the preferred method forsterilising the wound dressings of the invention after manufacture andprior to use. Either gamma-irradiation or electron-beam irradiation canbe used. The dressing can be irradiated by 25 kGy or more, or by loweramounts sufficient to achieve sterilisation. Surprisingly, it has beenfound that the ability of the honey layer to absorb liquid is diminishedsubstantially and to a similar degree by both gamma-irradiation andelectron-beam irradiation, if the ratio of moisture-absorbing agent tohoney is very low, i.e. in compositions containing a relatively lowproportion of moisture-absorbing agent. To ensure that the compositematerial retains its optimal properties, that is to say it issubstantially impervious to liquid water but permeable to water vapourand with good liquid absorbency, even after irradiation, it is preferredthat the weight ratio of moisture-absorbing agent to honey is in therange from 1:2 or 1:3 or 1:4 to 1:5. In preferred embodiments, theliquid absorbency is at least 15 g per 100 cm² after irradiation.

The identity of the moisture-absorbing agent and its molecular weightwill also affect the constitution of the honey mix, and the preciseidentity and molecular weight of the agent used for best results mayeasily be determined by experiment. The moisture-absorbing agent may beselected from those which are non-toxic and pharmaceutically acceptable.Suitable moisture-absorbing agents include alginate salts such as sodiumalginate (e.g. Keltone™ HVCR sodium alginate) and modified cellulosepolymers such as carboxymethylcellulose (CMC), generally in powder form.

The water-permeable fabric for the intermediate and backing layers ispreferably a needled non-woven fabric, but woven fabric may also beused. It is preferably a calcium alginate fabric, but other fabricmaterials such as carboxymethylcellulose or polyester may be used. Asmentioned above, the same fabric is preferably used for both layers. Thefabric density is preferably in the range 100 to 200, for example 150 to180 gsm (gm⁻²), although use of a lighter or heavier fabric may bepossible. However, with lighter weight fabrics, for example of 70 gsm orless, it may be more difficult to produce dressings substantiallyimpervious to liquid.

The amount of the mixture of honey and water-absorbing agent applied tothe water-permeable fabric is desirably in the range 1000 to 5000 gsm(gm⁻²), preferably 1500 to 4500 gsm, more preferably 2200 to 4200 gsm,although lower or higher amounts may be used. When the amount of themixture is substantially below 1500 gsm, for example down to 1350 gsm orless, the dressings may not be substantially impervious to liquid.

A particularly preferred dressing is composed of non-woven calciumalginate fabric of 130-170 gsm, preferably about 150 gsm, impregnatedwith 2000-3000 gsm, preferably about 2500 gsm, of a mixture of sodiumalginate and honey in a ratio by weight of 1:3 to 1:5, preferably about1:4, so as to form a wound-contacting layer of the sodium alginate/honeymixture, an intermediate layer of the fabric impregnated with the sodiumalginate/honey mixture and a backing layer of the fabric.

The dressings may also include one or more active pharmaceuticalcomponents to augment or supplement the properties of the dressing,particularly those components whose activity supplements those of honey,so that the wound-contacting layer need not be composed solely of honeyand the moisture-absorbing agent. For example, an antimicrobial agent,or an antibiotic, or an anaesthetic, or an anti-inflammatory agent, or awound-healing agent, or a skin-protective agent, or a substance intendedto negate malodours, can be incorporated. Suitable antimicrobial agentsinclude silver or silver-containing compounds, povidone iodine andsubstances or formulations which release hydrogen peroxide. Honeyalready contains an amount of glucose oxidase which acts in combinationwith glucose, also present in honey, to produce hydrogen peroxide.Additional amounts of glucose oxidase can be added artificially tosupplement this natural activity. Suitable anaesthetics includelidocaine hydrochloride. Suitable wound-healing agents include zincoxide.

The composite of honey-containing wound-contacting layer, intermediatelayer and fabric backing layer may be produced by mixing the honey andwater-absorbing agent batchwise or continuously in appropriateproportions, for example in an extruder such as a twin-screw extruder,for an appropriate period until a mixture is formed, extruding themixture at an appropriate temperature and calendering the extrudedmixture in contact with the fabric backing layer so as to achievepartial impregnation of the backing layer by the mixture. The mixing maybe carried out for from 2 to 60 minutes, a mixing period of 10 minutesor more being preferred to induce some degree of set in the mixture. Themixing temperature is preferably in the range 40 to 50° C. A final heattreatment to set the honey may be desirable. At heat settingtemperatures of about 80° C. setting occurs in less than 1 minute but at50° C. setting can take up to 30 minutes.

To create a self-adhesive wound dressing, an adhesive layer may beattached to or formed integrally with the fabric backing layer.Conveniently, the adhesive layer may extend laterally outwardly beyondthe periphery of the wound-contacting layer and is provided withadhesive material on such outward extension of its surface orientedtowards the wound-contacting layer. The adhesive layer may thereby becaused to adhere to an area of the skin of a patent to whom the dressingis supplied surrounding a wound to be treated, while the honey layer isbrought into contact with the wound. In preferred embodiments, theadhesive layer is disposed in a window-frame-type arrangement around theperiphery of the fabric backing sheet, leaving at least a substantialportion of the fabric backing sheet uncovered, i.e. not overlain by theadhesive layer. This arrangement has the advantage of allowing the wounddressing to “breathe”, thus permitting moisture absorbed in the honeylayer to be transpired to the atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereinafter be described in more detail, by way ofexample only, with reference to the accompanying drawing in which:

FIG. 1 is a diagrammatic representation of an embodiment of wounddressing according to the invention; and

FIG. 2 is a scanning electron microgram of a cross-section of a wounddressing manufactured according to the invention.

The stylised wound dressing depicted in FIG. 1 illustrates the basicstructure of an embodiment of wound dressing 10 according to theinvention, in which a fabric backing layer 12 is partially impregnatedwith a mixture of honey and sodium alginate to form an intermediatelayer 16, with the remainder of the honey/alginate mixture forming awound-contacting layer 14. A flexible adhesive fabric 18 is attached tothe periphery of the underside of the fabric layer 12 and is provided onits upper surface with an adhesive substance suitable for adhering thedressing to the patient's skin. The adhesive fabric 18 is mounted to thefabric backing layer 12 in a window-frame-type arrangement, leaving acentral hole 20, through which water vapour absorbed into the dressingis able to transpire.

The invention is further illustrated by reference to the followingExamples

EXAMPLE 1

A test sample of a composite three-layer structure according to theinvention was manufactured by the following procedure. 50 g of honey waswarmed to 50° C. and added to 10 g of Keltone™ HVCR sodium alginatepowder (viscosity 600-900 cP 1.25% aq. solution at 25° C. on spindle 3of an LV Brookfield viscometer at 60 rpm). The mixture was stirred for10 s and transferred to a petri dish. A disc of 150 gsm (gm−²) calciumalginate fabric was placed on top of the honey/sodium alginate mixture,followed by a closely fitting support member. The assembly was theninverted and placed under pressure to spread the honey/sodium alginatemixture evenly over the fabric carrier, and heated at 50° C. for 1 hour.The assembly was then cooled and the resulting composite productremoved. The sample was prepared for electron microscopy by immersion inliquid nitrogen and cut with a scalpel to produce a suitablecross-sectional surface, which was then coated with gold/palladium andanalysed under a Hitachi S4000 field emission scanning electronmicroscope operating at 2 kV. The resulting electron microgram appearsas FIG. 2 and clearly reveals a distinct three-layer structurecomprising (from left to right in the figure) honey layer, honey/fibreimpregnated layer, and fabric backing layer.

EXAMPLE 2

In order to test the fluid handling capabilities of dressingsmanufactured according to the invention, several further samples wereproduced, using varying ratios of sodium alginate to honey. The effectof gamma-irradiation was also studied. All of the samples were producedusing 150 gsm needled calcium alginate non-woven fabric carrier andKeltone™ HVCR sodium alginate powder. The weight ratio of alginatepowder to honey varied between 1:4 and 1:10. Half of the samples weregamma-irradiated (to 25 kGy) after manufacture. The samples weresubjected to the Paddington Cup test, and their liquid absorbency,moisture vapour transmission rate (“MVTR”—i.e. the mass of water vapourtranspired through the sample) and total fluid handling capacity(“TFHC”—i.e. the sum of MVTR and liquid absorbency) were measured interms of grams of water per 100 cm² surface area of sample per 24 hours.The results are set out in Table 1 below: TABLE 1 Non-IrradiatedIrradiated (25 kGy) g/m² of G/m² of sodium sodium Weight alginatealginate ratio of and and sodium honey honey alginate mixture mixture toin the in the honey dressing Absorbency MVTR TFHC dressing AbsorbencyMVTR TFHC 1:4  2251 44 43 87 2730 22 39 62 2578 43 42 86 2401 29 39 681:4  4660 53.5 24.1 77.6 4090 35.2 33.7 68.9 3516 52.8 33.1 85.9 387833.0 31.9 64.9 1:5  2259 40 45 85 2201 22 42 63 2622 51 46 96 2572 23 3962 1:5  3142 462 32.0 78.2 3504 18.7 36.0 54.7 3258 48.3 27.4 75.7 300019.9 37.8 57.7 1:5  3808 45.9 30.0 75.9 3437 22.2 32.4 54.6 3753 45.831.5 77.3 3491 19.7 36.7 56.4 1:5  3920 44.4 35.5 79.9 4153 19.1 26.545.6 4120 51.2 30.1 81.3 1:10 3067 46.1 37.4 83.5 3154 12.8 37.6 50.43079 34.6 33.5 68.1 3320 8.3 37.1 45.4

These results indicate that, in non-irradiated samples, all of thesamples demonstrated good liquid absorbency and TFHC and that variationsof alginate: honey weight ratio within the range 1:4 to 1:10 had littleeffect. Gamma-irradiation tended significantly to reduce liquidabsorbency as the amount of honey in the alginate/honey mixtureincreased.

Products were made with a honey sheet having a 1:4 sodium alginate:honey ratio and with (a) 150 gsm calcium alginate needled fabric and1350 gsm honey sheet, and (b) 70 gsm calcium alginate needled nonwovenfabric and 2500 gsm honey sheet, and these were gamma sterilized at 25kGy. They were subsequently tested using the Paddington Cup test and,after 24 hours, showed leakage of liquid through to the back of thedressing, i.e. they were not impervious to liquid, due to the “thinness”of the product, i.e. low honey level or low fabric density.

EXAMPLE 3

To test whether the identity of the fabric carrier had any effect onfluid handling capability, four samples were produced using a 1:5alginate:honey weight ratio, as before. Two of the samples weremanufactured using 150 gsm calcium alginate needled non-woven fabric andtwo using Hydrocel™ (carboxymethylcellulose) 100 gsm needled non-wovenfabric. Liquid absorbency, MVTR and TFHC after 24 hours were measured aspreviously, and the results are set out in Table 2 below: TABLE 2 Fabriccarrier type → Calcium Calcium Property ↓ alginate alginate CMC CMCWeight of Honey Sheet (g/m²) 3430 4190 4190 4100 Nice Dome Yes Yes YesYes 24 Hr absorbency g/100 cm² 44.0 40.0 43.0 39.0 24 Hr MVTR g/100 cm²31.0 28.0 27.0 29.0 24 Hr TFHC g/100 cm² 75.0 68.0 70.0 68.0

These results indicate that there is no significant difference betweenfabric carrier types or between sheet weights within the scope of thetests. The “dome” mentioned in the Table is a reference to the honeylayer swollen by absorption of saline, a “nice dome” therefore beingindicative, at least qualitatively, of good absorption.

EXAMPLE 4

A further test was carried out, using calcium alginate and polyester 150gsm needlebonded non-woven fabrics, to test fluid handling over anextended period (48 hours). The results are set out in Table 3 below:TABLE 3 Wt Fabric honey TFHC MVTR carrier sheet Absorbency Absorbencyg/100 cm² g/100 cm² type g/cm² g/100 cm²/24 hr g/100 cm²/48 hr 24 hr 48hr 24 hr 48 hr Alginate 3400 44 44 74 109 30 65 Polyester 3600 46 41 72101 26 60

These results demonstrate that liquid absorbency and vapour transmissionrate are maintained over a period of 48 hours, there being nosignificant difference in absorbency between the two fabrics over thatperiod.

EXAMPLE 5

16 kg of Manuka honey was placed into a Z-blade mixer with front andrear blades rotating at 32 rpm and 25 rpm respectively and with acirculating water jacket at 55° C. After 30 minutes, when the honey hadreached a temperature of 45° C., 4 kg sodium alginate powder (Keltone™HCVR) was added to the mixer over a 2-minute period. After a further 3.5minutes, by which time the honey mixture was homogeneous and had reacheda temperature of 48° C., the mixture was extruded through a fish-taildevice by means of a screw feeder rotating at 2.5 rpm. The extrudedsheet of honey mixture was 1.2 mm thick and was laid onto a supportpaper and then passed through calender rolls, heated to 55° C. bycirculating water, with a gap set to produce the required finalthickness of material. Prior to passing the extruded material throughthe calender rolls, 150 gsm calcium alginate needled nonwoven fabric,together with a backing release paper, was placed directly against thehoney mixture. The action of the calender rolls was to achieve partialimpregnation of the alginate fabric with the honey mixture. A final heattreatment, at 50° C. for 1 hour, set the honey mixture.

The above Example was repeated but this time allowing 30 minutes mixingtime for the honey and powder, in order to induce a degree of set priorto extrusion. It was found that setting of the honey mixture wasachieved without the need for a final heating treatment.

EXAMPLE 6

Instead of the batch operation described in Example 5, continuous mixingcan be employed. A twin-screw extruder having a series of temperaturezones down its length can be fed with sodium alginate powder togetherwith downstream addition of honey at one or more injection points andmixing and heating to a series of temperature points carried out toproduce a consistent mixture at a high temperature, for example of75-80° C., so that it would start to gel immediately on extrusion, andfed to forming and calendering equipment similar to that alreadydescribed in Example 5. Optimisation of the temperature profile enablesthe final heat treatment to set the honey mixture to be omitted.

1. A wound dressing having honey and a moisture-absorbing agent,comprising a wound-contacting layer including a mixture of honey and amoisture-absorbing agent; a water-permeable fabric backing layer; and anintermediate layer comprising water-permeable fabric impregnated with amixture of honey and a moisture-absorbing agent.
 2. A wound dressingaccording to claim 1, wherein said dressing is substantially imperviousto liquid water but substantially permeable to water vapour.
 3. A wounddressing according to claim 2, wherein said dressing remainssubstantially impervious to liquid water but substantially permeable towater vapour even after gamma-irradiation. 4-18. (canceled).
 19. Amethod of manufacturing a wound dressing, comprising the steps of:providing a layer of a water-permeable fabric material; providing amixture of honey and a moisture-absorbing agent; spreading said mixtureover said fabric layer; allowing a portion of said mixture to impregnatean upper sub-layer of said fabric layer; and allowing said mixture toset, thereby to produce a dressing comprising a wound-contacting layerincluding a mixture of honey and a moisture-absorbing agent, awater-permeable fabric backing layer, and an intermediate layercomprising fabric impregnated with said mixture of honey andmoisture-absorbing agent.
 20. A method according to claim 19, whereinsaid mixture of honey and moisture-absorbing agent is allowed toimpregnate said fabric layer to a depth of 100 μm to 1,000 μm. 21-23.(canceled).
 24. A method according to claim 19, further comprising thestep of attaching to said fabric layer an adhesive layer extendinglaterally outwardly beyond a periphery of said wound-contacting layerand being provided with adhesive material on such outward extension ofits surface oriented towards said wound-contacting layer to provideadhesion of said adhesive layer to an area of skin of a patient to whomthe dressing is applied, surrounding a wound to be treated.
 25. A methodaccording to claim 24, wherein said adhesive layer does not overlie atleast a substantial portion of said fabric layer.
 26. A method accordingto claim 19, further comprising the step of subjecting the dressing togamma-irradiation.
 27. A method according to claim 19, wherein themixture of honey and the moisture-absorbing agent is provided bycontinuous mixing in a twin-screw extruder.
 28. A method according claim27, wherein said mixing is carried out in a twin-screw extruder having aseries of temperature zones down a length of said extruder.
 29. A methodaccording to claim 27, wherein the mixture of honey and themoisture-absorbing agent is provided at a temperature such that gellingstarts to occur immediately on extrusion through said twin-screwextruder.
 30. A method according to claim 27, wherein the mixture ofhoney and the moisture-absorbing agent is provided at a temperature ofabout 75° C. to about 80° C.
 31. A method according to claim 27, whereinthe mixture of honey and the moisture-absorbing agent is laid onto asupport paper.
 32. A method according to claim 31, wherein the mixtureof honey and the moisture-absorbing agent laid onto the support paper ispassed in direct contact with the layer of the water-permeable fabricmaterial through calendar rolls, to thereby achieve partial impregnationof the fabric material with the mixture.
 33. A method according to claim32, wherein the layer of the water-permeable fabric material is passedthrough calendar rolls together with a backing release paper.
 34. Awound dressing according to claim 1, wherein an identity of saidmoisture-absorbing agent and a ratio of honey with respect to said agentare chosen so that said wound-contacting layer forms a substantiallyhomogeneous solid sheet.
 35. A wound dressing according to claim 1,wherein said wound-contacting layer and said intermediate layer form afirst continuous phase, and wherein said fabric layer and saidintermediate layer form a second continuous phase, said first and secondcontinuous phases overlapping to form said intermediate layer.
 36. Awound dressing according to claim 35, wherein said intermediate layerhas a thickness of between 100 μm and 1,000 μm.
 37. A wound dressingaccording to claim 36, wherein said intermediate layer has a thicknessof between 200 μm and 500 μm.
 38. A wound dressing according to claim35, wherein said wound-contacting layer is free from fabric and saidfabric layer is free from honey.
 39. A wound dressing according to claim1, wherein a weight ratio of moisture-absorbing agent to honey in saidwound-contacting and intermediate layers is between 1:2 and 1:14.
 40. Awound dressing according to claim 39, wherein said ratio is in the range1:4 to 1:10.
 41. A wound dressing according to claim 40, wherein saidratio is in the range 1:4 to 1:5.
 42. A wound dressing according toclaim 1, wherein said moisture-absorbing agent is an alginate orcarboxymethyl cellulose powder.
 43. A wound dressing according to claim42, wherein said moisture-absorbing agent is sodium alginate.
 44. Awound dressing according to claim 1, wherein said dressing has a 24-hourmoisture vapour transmission rate of at least 20 g per 100 cm² and a24-hour total fluid handling capacity of at least 35 g per 100 cm². 45.A wound dressing according to claim 1, further comprising an adhesivelayer attached to or integral with said fabric backing layer, saidadhesive layer extending laterally outwardly beyond a periphery of saidwound-contacting layer and being provided with adhesive material on suchoutward extension of its surface oriented towards said wound contactinglayer to provide adhesion of said adhesive layer to an area of skin of apatient to whom the dressing is applied, surrounding a wound to betreated.
 46. A wound dressing according to claim 45, wherein at least asubstantial portion of the fabric backing layer is not overlain by saidadhesive layer.
 47. A wound dressing according to claim 1, wherein thedressing has been gamma-irradiated.
 48. A wound dressing according toclaim 47, wherein the dressing is gamma-irradiated by at least 25 kGy.